Potassium fluoride is useful as a fluorinating agent for an organic compound. WP1987/004151 discloses that a method comprising preparing a potassium fluoride dispersion by mixing potassium fluoride with about 1.4 parts by weight of methanol per 1 parts by weight of potassium fluoride and sulfolane followed by concentrating methanol from the obtained mixture, and fluorinating an organic compound using the prepared potassium fluoride dispersion. However, an activity of the potassium fluoride dispersion in a fluorination reaction is not necessarily enough and it is necessary to conduct a fluorination reaction using an expensive phase transfer catalyst.